Properties of modern AFL can be characterized according to the results of standard aircompanies’tests due to the following patterns: absence of mechanical mixtures; time of stability to icing (depending on concentration and out-doors temperatures) - from 40 minutes to 10 hours; length of boundary shift layer - from 8 to 11 mm; hydrogen index (pH) – pH=9,5±0,5; density from 1,094 to 1,102 gr/cubic sm under the temperature of 20 Celsius degrees; temperature of crystallization - not more than -50 Celsius degrees; mass share of anti-corrosion additive - 0,5-0,6%; dynamic surface tension - not more than 40 mN/m; kinematical viscidity under the temperature of 20 Celsius degrees not less than 9 square mm/s.
The most difficult among these items is to fix dynamic AFL surface tension. The following device is proposed for examination (picture 1). It consists of a stalagmometer (1), covered in a glass casing (2) by rubber corks (3). To regulate the speed of liquid expiration to the upper end of the stalagmometer there is a rubber tube (5) with a spiral clamp (6). The stalagmometer presents a thick-sided glass tube with one or two expands in the middle of it in the form of spherical reservoirs. In the bottom of the tube there is a capillary with an internal diameter of 0, 7-1, 0 mm. The lower ground of the tube must be polished strictly perpendicularly to the axial line of capillary for an even formation of drop and tearing it away from a stalagmometer.
Picture 1. The scheme of the device for determination of dynamic surface tension of AFL:
1 - a stalagmometer; 2 - a glass casing; 3 - rubber corks; 4 - union couplings for joining a glass covering to ultra-thermostat;
5 - a rubber tube (d = 5 mm, l = 50-60 mm); 6 - a spiral clamp.
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